42 



THE AGE OF MAMMALS 



Africa 



Upper 



Oligocene i Middle 



Lower 



' Upper 



Middle 



Eocene 



Lower 



• Basal 



Cretaceous Uppermost 



Fayum 



Fayura 



Aquitanian 



Stampian 



Sannoisian 



LUDIAN 



Bartonian 

 Lutetian 



Upper Ypresian 



Lower Ypresian 



Sparnacian 



(Upper Landenian of Bel- 

 gium) 



Upper Thanetian ( = Cer- 

 naysian) 

 (Lower Landenian of Bel- 

 gium) 



Lower Thanetian 



Danian = Maestrichtian 

 (Terrestrial) (Marine) 



Harrison (Lower) 

 John Day 

 White River 



(Upper) 

 Wliite River 



(Middle) Brule 



Clays 

 Wliite River(Base) 

 Cypress Hills 

 Pipestone Creek 

 _ Chadron 



I Uinta (Upper and 

 Middle) 

 Washakie (Upper) 

 i Uinta (Lower) 

 Washakie (Lower) 

 Bridger (Upper) 

 J Bridger (Lower) 

 1 Huerfano (Upper) 



(Bridger (Lower) 

 Huerfano (Upper) 

 Green River 

 (Huerfano (Lower) 

 Wind River 

 Wasatch (LTpper) 

 Wasatch (Lower) 



I Torrejon 

 1 Fort Union 



[ Puerco 



[ Fort LTnion 



Hell Creek 



Importance of Time Correlation 



If we are eager to solve the great number and variety of most inter- 

 esting questions still unsolved as to the source, origin, affiliation, migra- 

 tion, and extinction of the noble races of animals which passed across the 

 stage of the northern hemisphere, or ancient Holarctic Region, during the 

 Csenozoic Period, we must endeavor to use very exact methods of com- 



